1. Field of the Invention
The present invention relates to an optical fiber connector assembled to a front end portion of an optical transmission medium such as an optical fiber cord or an optical fiber cable and a method of assembling the optical fiber connector, and more particularly, to an optical fiber connector in which a front end portion of an optical transmission medium is optically connected to an optical fiber (short optical fiber) inserted into a ferrule by fusion splice between optical fibers, a method of assembling an optical fiber connector, a method of reinforcing a fusion-spliced portion of optical fibers which can be suitably used for the optical fiber connector, an optical fiber connector assembling tool, and an optical fiber connector assembling set.
The present invention also relates to an optical fiber connector assembled to a front end portion of an optical transmission medium such as an optical fiber cord or an optical fiber cable, a pin clamp used therein, and a method of assembling the optical fiber connector.
The present invention also relates to an optical fiber connector cap which is detachably attached to the housing of an optical fiber connector when assembling the optical fiber connector to a terminal of an optical transmission medium such as an optical fiber cord or an optical fiber cable in which an optical fiber and a fiber-like tensile member extending along the optical fiber is covered with a sheath and which is used for assembly work of the optical fiber connector.
2. Background Art
In the past, an optical fiber connector having built therein a mechanical splice mechanism interposing an inserted optical fiber, one end of which is fixed to a ferrule and an optical fiber of an external optical transmission medium, between two divided parts in a state where they are butt-jointed to each other and maintaining the butt-jointed state was known as an example of an optical fiber connector enabling a work of assembling an optical fiber connector to an end portion of an optical transmission medium such as an optical fiber cord or an optical fiber cable to be carried out on a splicing site (for example, see Japanese Unexamined Patent Application, First Publication No. 2002-196189).
An optical fiber connector connecting an optical fiber of an optical transmission medium and an optical fiber built in a ferrule of the optical fiber connector to each other by fusion was also known (for example, see U.S. Pat. No. 5,748,819 and Japanese Unexamined Patent Application, First Publication No. 2008-65315). Japanese Unexamined Patent Application, First Publication No. 2002-196189 (particularly, paragraphs 0022 to 0024 and FIGS. 1 to 4) discloses an optical fiber connector precisely positioning optical fibers between two divided elements having an alignment groove (a V groove, a U groove, or the like) used to align optical fibers and butt-jointing the optical fibers.
U.S. Pat. No. 5,748,819 (particularly, FIGS. 1 to 3) discloses an optical fiber connector having a structure in which a fusion-spliced portion is disposed in a slot formed in a ferrule, a front end of a built-in optical fiber is located on an end face, and a rear end of the built-in optical fiber is exposed into the slot so as to be fusion-spliced to an end of an optical fiber of an optical transmission medium in the slot.
Japanese Unexamined Patent Application, First Publication No. 2008-65315 (particularly, paragraphs 0033 to 0036 and FIGS. 3 and 4) discloses an optical fiber connector in which an end of an optical fiber of which the other end is fixed to a ferrule is fusion-spliced to an end of an optical fiber core and the fusion-spliced portion is reinforced with a reinforcing member such as a heat-shrinkable sleeve or a metal sleeve.
An optical fiber connector configured to splice an inserted optical fiber of which an end portion is fixed to a ferrule and an optical fiber of an external optical transmission medium to each other by fusion or the like was known as an example of an optical fiber connector enabling a work of assembling an optical fiber connector to a front end portion of an optical transmission medium such as an optical fiber cord or an optical fiber cable to be carried out on a splicing site (for example, see Japanese Unexamined Patent Application, First Publication No. 2002-196189 and Japanese Unexamined Patent Application, First Publication No. H10-319275).
An example of such a type of optical fiber connector is a multi-core optical fiber connector (an MPO type optical fiber connector; MPO: Multi-fiber Push On) defined in the JIS C5982 or the like.
When butt-jointing the optical fiber connectors to each other, a guide pin protruding from a joint end face of a ferrule of one optical fiber connector is inserted into and locked to a guide pin insertion hole of a joint end face of a ferrule of the other optical fiber connector. Accordingly, the ferrules are positioned with a high precision.
One optical fiber connector is of a male type having a guide pin and the other optical fiber connector is of a female type not having a guide pin.
The guide pin is inserted into a guide pin insertion hole formed in the ferrule and then the rear end portion thereof is supported by a pin clamp formed in the back of the ferrule.
When assembling an optical fiber connector to an optical fiber cord terminal extending a tensile fiber has been carried out, which is longitudinally added to an optical fiber of an optical fiber cord and is received in a sheath along with the optical fiber, to a cord terminal and to fix the tensile fiber to the rear end of the body (housing) of the optical fiber connector with a metal ring by swaging so as to satisfactorily detain the optical fiber cord in the optical fiber connector (for example, see Japanese Unexamined Patent Application, First Publication No. 2001-235656).
The optical fiber connector disclosed in Japanese Unexamined Patent Application, First Publication No. 2002-196189 does not require an alignment groove to position optical fibers relative to each other before splicing. Accordingly, the decrease in cost is limited due to the presence of components to be machined by high-precision processing.
The optical fiber connector disclosed in U.S. Pat. No. 5,748,819 requires fusion work at a side surface position of a ferrule. Accordingly, when a general-purpose discharging electrode is used in the fusion work, the ferrule may be adversely affected and thus a general fusion splicer should not be used, thereby making the fusion work difficult.
In the optical fiber connector disclosed in Japanese Unexamined Patent Application, First Publication No. 2008-65315, the other end of the optical fiber fixed to the ferrule is drawn out from the ferrule, the adverse influence of the fusion work on the ferrule is reduced. However, since the reinforcing sleeve needs to pass the optical fiber core therethrough before the fusion work and to move to a position where it covers the outer circumference of the fusion-spliced portion after the fusion work, it takes much labor to form a splice reinforcing portion. The outer diameter of the optical fiber core needs to be smaller than the inner diameter of the sleeve (so that the outer circumferential shape of the sectional surface of the optical fiber core is included in the inner circumferential shape of the sectional surface of the sleeve). Accordingly, it is difficult to apply this technique to an optical transmission medium such as a drop cable or a multi-core optical fiber having a large outer diameter (outer circumferential shape).
In order to enhance the efficiency of the work on the splicing work site, there is a need for an optical fiber connector having a structure capable of selecting the presence or absence of a guide pin (male type or female type).
In the optical fiber connector, the guide pin can be attached and detached by inserting or pulling the guide pin, the rear end portion of which is fixed to a pin clamp, into or from the rear side thereof.
However, it is not possible to avoid the increase in size of the optical fiber connector, in that it is substantially difficult to attach and detach the guide pin in consideration of the adverse influence on an optical fiber spliced portion (for example, a fusion-spliced portion) and it is necessary to guarantee a space for movement of the pin clamp between the ferrule and the optical fiber spliced portion so as to avoid the adverse influence.
When the optical fiber connector is configured to weaken the fixing force in the rear end of the guide pin and to be able to easily insert or pull the guide pin into or from the front side of the ferrule, the space on the rear side of the ferrule is not necessary, but there is a problem in that the guide pin can easily fall out with this structure.
When performing the work of fixing the tensile fiber to the body of the optical fiber connector by swaging, it is necessary to swage a metal ring in a state where tension is applied to the tensile fiber. Accordingly, for example, as disclosed in Japanese Unexamined Patent Application, First Publication No. 2001-235656, a tool (hereinafter, also referred to as a swaging tool) capable of fixing the optical fiber connector and the optical fiber cord and fixing the tensile fiber extending from the cord terminal is necessary. The labor of fixing the optical fiber connector, the optical fiber cord, and the tensile fiber extending from the cord terminal by the use of the swaging tool is necessary.